Coryphantha cornifera
| Light | Bright light with some protection from the harshest afternoon sun |
|---|---|
| Water | Moderate in the growing season, allowing the mix to dry out fully; keep dry in winter |
| Soil | Gritty, fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; roughly USDA zones 9b–11 |
| Propagation | Seed |
| Toxicity | Non-toxic to cats and dogs |
Coryphantha cornifera is a solitary, globe-shaped cactus from central Mexico, best known for the stout, curving central spine that tips each tubercle like a small horn. That distinctive horn-like spine, borne on a firm grey-green body, has earned it the common name rhinoceros cactus, and in summer the plant is crowned by comparatively large, glossy yellow flowers. It belongs to the genus Coryphantha, a group of tuberculate cacti closely allied to Mammillaria.
Description
Coryphantha cornifera is usually solitary, forming a rounded to shortly cylindrical body up to around 12 cm across, though plants are often smaller in cultivation. The surface is broken into prominent conical tubercles arranged in spirals, each carrying a woolly areole at its tip. Like other members of the genus, it has a groove running along the upper face of each mature tubercle — a feature that helps separate Coryphantha from the closely related Mammillaria.
The spination is the plant's signature. Each areole bears a spreading ring of stiff radial spines and, at the centre, a stout central spine — occasionally two or three — that curves like a horn or claw. Flowers appear from the growing crown in summer: broad, funnel-shaped and a bright, satiny yellow, often several centimetres across and large in proportion to the body.
Distribution and habitat
The species is native to central Mexico, where it grows on limestone hills and in open, arid scrub and grassland. Plants typically root in rocky or gritty ground among low vegetation that offers a little seasonal shade, enduring hot dry spells and cooler, drier winters. As with the whole cactus family, wild Coryphantha are listed under CITES Appendix II; nursery-grown plants are widely available and are the responsible choice for collectors.
Cultivation
Coryphantha cornifera is a fairly straightforward plant for anyone already growing globular cacti, its main enemy being excess moisture. Grow it in a very free-draining, mostly mineral mix in a pot that drains freely, and give it bright light — plenty of sun brings out strong spination and encourages flowering, though a little shade from the fiercest afternoon glare in the hottest climates does no harm.
Water thoroughly during the warm growing months once the mix has dried out, then allow it to dry again before the next watering. Through winter, keep the plant cool and essentially dry; this winter rest both protects against rot and helps set the following season's flowers. See Watering and Repotting for general technique.
Propagation
Because the species is normally solitary and seldom offsets, seed is the usual means of propagation. Sow onto a warm, gritty surface kept humid until germination, then grow the seedlings on slowly and pot up as they establish. See Propagation — seed for a full walkthrough. On the rare occasion a plant produces an offset it can be removed and rooted as for other clustering cacti (see Propagation — offsets).
Common problems
- Rot — the most common cause of loss, almost always from overwatering or a mix that holds too much moisture; the body softens and discolours, usually from the base.
- Etiolation — too little light makes the body pale and stretch, weakening the characteristic spination and symmetry.
- Pests — red spider mites (fine webbing and bronzed skin) and mealybugs (white fluff tucked into the areoles and between tubercles) are the usual offenders. See Pests and diseases.
See also
- Coryphantha — the genus overview
- Mammillaria — a closely related tuberculate genus
- Soil and potting mix · Watering · Repotting · Propagation — seed · Pests and diseases